Acrylic polymers have many useful properties such as durability, flexibility in composition and glass transition temperature (xe2x80x9cTgxe2x80x9d), weather resistance, adhesion to polar substrates, and compatibility with many polar polymers and inoganic components. While each of the properties may be desirable, it is difficult to obtain all of them in one polymer. One often needs to sacrifice one property to gain another because the properties of the polymer depend on the polymer""s composition, molecular weight, and Tg. For example, a low Tg may be desirable for a polymer composition which would be useful in adhesive applications, but the low Tg polymer may not provide good durability.
In addition, because acrylic polymers are generally amorphous, they are not effective in all applications where crystallinity is desired. They do not adhere well to most non-polar substrates such as polyolefins. Amorphous acrylic polymers also are inferior in terms of water resistance and durability as compared with polyolefins. Therefore, there is a need for low cost polymer compositions which provide durability, flexibility in composition and Tg, weather resistance, adhesion to polar and non-polar substrates, compatibility with polar polymers and inoganic components, and water resistance.
Previous methods to achieve a combination of desired properties of acrylic polymers and olefin polymers in xe2x80x9conexe2x80x9d polymer included physically mixing an acrylic polymer and an olefin polymer or copolymerizing an olefin monomer and an acrylic monomer. These methods have not been successful. Physical mixing of acrylic polymers and polyolefins does not usually yield useful compositions because the two polymers are incompatibile. Copolymerizing an olefin monomer and an acrylic monomer is difficult because there is poor reactivity between the two monomers. In addition, copolymerization of two monomers usually results in a composition with an average of the combined properties of each homopolymer rather than enhanced properties.
U.S. Pat. No. 5,387,450 (""450) tries to solve the problem. This patent discloses polymer compositions which contain as polymerized units crystallizable side chain monomers and are useful as adhesives. Below the melting temperature of the crystallizable side chain, the polymer is non-tacky. Above the melting temperature of the crystallizable side chain, the polymer turns into a tacky adhesive. The compositions are required to contain at least 50 weight percent of a crystallizable side chain monomer. The crystallizable side chain monomers are acrylates or methacrylates with 14 to 22 carbon atoms as side chains. Even though this patent provides a route to achieve some of the properties discussed above, there are still several problems unresolved by the patent. The crystallizable side chain monomers of the patent have lower melting points and are more soluble in organic solvents than crystallizable side chain monomers with more carbon atoms in the side chains. Therefore, one problem is that the patent does not address how to process crystallizable side chain monomers with more carbon atoms in the side chains, which require higher temperatures to melt and are less soluble in organic solvents. Another problem is that crystallizable side chain monomers are relatively new and due to their special structure are estimated to cost several times more than the other monomeric components. For these reasons, it is desirable to minimize the amount of crystallizable side chain monomer in one polymer and still achieve the properties described above. Despite the disclosure of ""450, there is still a need for low cost polymer compositions which provide durability, flexibility in composition and Tg, weather resistance, adhesion to polar and non-polar substrates, compatibility with polar polymers and inoganic components, and water resistance.
To provide the desired polymer compositions, the inventors have prepared polymers containing an acrylic backbone with less than 50 percent by weight synthetic wax monomer (xe2x80x9cSWMxe2x80x9d). The SWM contains crystalline polyethylene side chains and therefore is a crystallizable side chain monomer. One benefit from the copolymers of this invention is that one may achieve physical crosslinking through the association of one polymer component. This association can be crystallization or simply phase separation. The physical crosslinks that form are not permanent and can be xe2x80x9cdecrosslinkedxe2x80x9d by heating. Through such physical crosslinking, the backbone polymer matrix forms a network like structure, yet it can be fully decrosslinked when the polymer is heated above the melting temperature of the association blocks. Formation of a network structure helps to prevent loss of the physical properties when one has to reduce the molecular weight or Tg of the backbone polymer for processing or flexibility reasons.
In a first aspect, the present invention provides a polymer including as polymerized units:
A) from 1 to less than 50 percent by weight of a synthetic wax monomer of formula I: 
xe2x80x83wherein
R1 is selected from H and CH3,
R2 is selected from H and C1-C5 alkyl,
R3 is selected from H and CH3,
n=9-115, preferably 12-90, more preferably 15-50, and
m=0-1370, preferably 0-65, more preferably 0-50; and
B) from 50 to 99 percent by weight of at least one second monomer.
Previously, it has been difficult to prepare the polymer compositions described above. For example, the ""450 patent described above utilized a one shot solution polymerization reaction to polymerize the monomers. For a solution process, it is desirable to be able to gradually add the SWM to the polymerization kettle because it is believed that the SWM will be more evenly incorporated into the polymer. Emulsion and suspension processes are desirable because they allow for a reduction of or elimination of organic solvents. The ""450 patent did not address these concerns. Consequently, there is a continuing need for processes to prepare polymers containing SWMs.
The inventors have provided several approaches to preparing polymers containing SWMs. In one approach, a SWM slurry is prepared prior to polymerization of the SWM. The slurry may be used to prepare solution or suspension polymers. For a solution process, the slurry may be combined with additional monomers or organic solvent and co-fed to a reactor with an initiator. For a suspension process, the slurry is combined with an initiator and an aqueous solution and polymerized.
In a second aspect, the present invention provides a method of preparing a polymer from a slurry by: 1) forming a slurry by cooling a solution containing a synthetic wax monomer and a solvent; 2) forming a reaction mixture by admixing at least one second monomer with the slurry; and 3) polymerizing the reaction mixture in the presence of an initiator.
In a third aspect, the present invention provides a method of preparing a polymer from an emulsion by dissolving a synthetic wax monomer in at least one second monomer to form a solution, admixing water and at least one surfactant to provide a second solution, forming a monomer emulsion by admixing the first and second solutions, providing a reactor with heated water, and polymerizing the monomer emulsion by adding the monomer emulsion and at least one initiator to the reactor.
In a fourth aspect, the present invention provides a method of coating including applying a composition containing the polymer of the invention to a substrate.
As used throughout this specification, by the term (meth)acrylic acid is meant both acrylic acid and methacrylic acid. Likewise, as used throughout this specification, by the term (meth)acrylate is meant both acrylate and methacrylate esters.
The SWMs of this invention are C24 to C80, preferably C30 to C50 ethylenically unsaturated (meth)acrylate monomers or ethoxylates thereof and are formed from C24 to C80 synthetic wax alcohols. Generally, the SWMs are formed by reacting a C24 to C80 synthetic wax alcohol or ethoxylate thereof with an alkyl(meth)acrylate in the presence of a zirconium catalyst and suitable inhibitor, although they may be made by other processes well known in the art. Suitable alcohols or ethoxylates are available from Baker Petrolite, Inc. Houston, Tex. as Unilin(trademark) or Unithox(trademark) products. Suitable examples of SWMs include the acrylate or methacrylate esters of Unilin 350, Unilin 450, Unilin 550, Unilin 700, and Unithox 450. The amount of SWM in the polymer is typically from 1% to less than 50%, preferably 3% to 45%, more preferably 4% to 40%, most preferably 5% to 35% by weight, based on the total weight of the polymer of this invention.
The at least one second monomer may be an ethylenically unsaturated monomer. Suitable ethylenically unsaturated monomers include acrylic and methacrylic acid and esters thereof. Generally, the (meth)acrylates are C1 to C24 (meth)acrylates. The (meth)acrylate is typically from 50% to 99%, preferably 55% to 97%, more preferably 60% to 96% by weight, based on the total weight of the polymer of the composition of this invention. Examples of the alkyl(meth)acrylate are methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl and ethyl acrylate, propyl methacrylate, butyl methacrylate (BMA) and acrylate (BA), isobutyl methacrylate (IBMA), hexyl and cyclohexyl methacrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate (EHA), 2-ethylhexyl meth-acrylate, octyl methacrylate, decyl methacrylate, isodecyl methacrylate (IDMA, based on branched (C10)alkyl isomer mixture), undecyl methacrylate, dodecyl methacrylate (also known as lauryl methacrylate), tridecyl methacrylate, tetradecyl methacrylate (also known as myristyl methacrylate), pentadecyl methacrylate, dodecyl-pentadecyl methacrylate (DPMA), a mixture of linear and branched isomers of dodecyl, tridecyl, tetradecyl and pentadecyl methacrylates; and lauryl-myristyl methacrylate (LMA), a mixture of dodecyl and tetradecyl methacrylates, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, cosyl methacrylate, eicosyl methacrylate, cetyl-eicosyl methacrylate (CEMA), a mixture of hexadecyl, octadecyl, cosyl and eicosyl methacrylate; and cetyl-stearyl methacrylate (SMA), and a mixture of hexadecyl and octadecyl methacrylate. Mixtures of one or more (meth)acrylates may also be used.
Another class of suitable ethylenically unsaturated monomers useful as the at least one second monomer are vinylaromatic monomers which include, among others, styrene (Sty), xcex1-methylstyrene, vinyltoluene, p-methylstyrene, ethylvinylbenzene, vinylnaphthalene, vinylxylenes, and the like. The vinylaromatic monomers can also include their corresponding substituted counterparts, such as halogenated derivatives, i.e., containing one or more halogen groups, such as fluorine, chlorine or bromine; and nitro, cyano, alkoxy, haloalkyl, carbalkoxy, carboxy, amino, alkylamino derivatives and the like. The vinylaromatic monomers may be used at levels of from 0% to 50%, preferably 0% to 30% by weight, based on the total weight of the polymer of the composition of this invention.
Another class of suitable ethylenically unsaturated monomers that may be useful as the at least one second monomer are nitrogen-containing ring compounds and their thioanalogs, such as vinylpyridines such as 2-vinylpyridine or 4-vinylpyridine, and lower alkyl (C1-C8) substituted C-vinyl pyridines such as: 2-methyl-5-vinyl-pyridine, 2-ethyl-5-vinylpyridine, 3-methyl-5-vinylpyridine, 2,3-dimethyl-5-vinyl-pyridine, 2-methyl-3-ethyl-5-vinylpyridine; methyl-substituted quinolines and isoquinolines, N-vinylcaprolactam, N-vinylbutyrolactam, N-vinylpyrrolidone, vinyl imidazole, N-vinyl carbazole, N-vinyl-succinimide, acrylonitrile, o-, m-, or p-aminostyrene, maleimide, N-vinyl-oxazolidone, N,N-dimethyl aminoethyl-vinyl-ether, ethyl-2-cyano acrylate, vinyl acetonitrile, N-vinylphthalimide. Also included are N-vinyl-thio-pyrrolidone, 3methyl-1-vinyl-pyrrolidone, 4-methyl-1-vinyl-pyrrolidone, 5-methyl-1-vinyl-pyrrolidone, 3-ethyl-1-vinyl-pyrrolidone, 3-butyl-1-vinyl-pyrrolidone, 3,3-dimethyl-1-vinyl-pyrrolidone, 4,5-dimethyl-1-vinyl-pyrrolidone, 5,5-dimethyl-1-vinyl-pyrrolidone, 3,3,5-trimethyl-1-vinyl-pyrrolidone, 4-ethyl-1-vinyl-pyrrolidone, 5-methyl-5-ethyl-1-vinyl-pyrrolidone, 3,4,5-trimethyl-1-vinyl-pyrrolidone, and other lower alkyl substituted N-vinyl-pyrrolidones. The nitrogen-containing ring compounds and their thioanalogs may be used at levels of from 0% to 50%, preferably 0% to 30% by weight, based on the total weight of the polymer of the composition of this invention.
Another class of suitable ethylenically unsaturated monomers that may be useful as the at least one second monomer are substituted ethylene monomers, such as vinyl acetate, vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, vinylidene fluoride, vinylidene bromide, acrylonitrile, methacrylonitrile, acrylic acid (AA) and corresponding amides and esters, methacrylic acid (MAA) and corresponding amides and esters. The substituted ethylene monomers may be used at levels of from 0% to 50%, preferably 0% to 30% by weight, based on the total weight of the polymer of the composition of this invention.
Another class of acrylic and methacrylic acid derivatives that may be useful as the at least one second monomer is represented by substituted alkyl acrylate and methacrylate and substituted acrylamide and methacrylamide monomers. Examples include (meth)acrylates wherein the alkyl group is substituted with halogen, such as fluorine, chlorine or bromine; and nitro, cyano, alkoxy, haloalkyl, carbalkoxy, carboxy, amino, alkylamino derivatives, glycidyl(meth)acrylate and the like. The substituted alkyl acrylate and methacrylate and substituted acrylamide and methacrylamide monomers may be used at levels of from 0% to 50%, preferably 0% to 30% by weight, based on the total weight of the polymer of the composition of this invention.
Each of the substituted monomers that may be useful as the at least one second monomer can be a single monomer or a mixture having different numbers of carbon atoms in the alkyl portion. The alkyl portion of each monomer can be linear or branched.
Hydroxyalkyl(meth)acrylate monomers may also be useful in this invention as the at least one second monomer. Among the hydroxyalkyl methacrylate and acrylate monomers suitable for use in the present invention are 2-hydroxyethyl methacrylate (HEMA), 2-hydroxyethyl acrylate(HEA), 2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate, 2-hydroxy-propyl acrylate, 1-methyl-2-hydroxyethyl acrylate, 2-hydroxybutyl methacrylate and 2-hydroxybutyl acrylate. The hydroxyalkyl(meth)acrylate monomers may be used at levels of from 0% to 50%, preferably 0% to 30% by weight, based on the total weight of the polymer of the composition of this invention.
Additional examples of substituted (meth)acrylate monomers useful as the at least-one second monomer are those alkyl methacrylate and acrylate monomers with a dialkylamino group in the alkyl radical, such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate and the like.
Other examples of substituted (meth)acrylate monomers useful as the at least one second monomer are nitrogen-containing ring compounds (previously described) and dialkylaminoalkyl methacrylamide and acrylamide monomers, such as N,N-dimethylaminoethyl methacrylamide, N,N-dimethyl-aminopropyl methacrylamide, N,N-dimethylaminobutyl methacrylamide, N,N-diethylaminoethyl methacrylamide, N,N-diethylaminopropyl methacrylamide, N,N-diethylaminobutyl methacrylamide, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-(1,3-diphenyl-1-ethyl-3-oxobutyl)acrylamide, N-(1-methyl-1-phenyl-3-oxobutyl)methacrylamide, and 2-hydroxyethyl acrylamide, N-methacrylamide of aminoethyl ethylene urea, N-methacryloxy ethyl morpholine, N-maleimide of dimethylaminopropylamine and the like.
Ethylenically unsaturated acid monomers such as, for example acrylic acid, methacrylic acid, crotonic acid, phosphoethyl methacrylate, 2-acrylamido-2-methyl-1-propanesulfonic acid, sodium vinyl sulfonate, itaconic acid, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, and maleic anhydride may also be used as the at least one second monomer in the polymers of this invention. The ethylenically unsaturated acid monomers may be used at from 0%-20% by weight, based on the weight of the polymer.
The polymer of this invention can be linear, branched or partially crosslinked. It can be post crosslinkable. By post crosslinkable is meant that the polymer may have reactive groups which do not react during polymerization, but may react after polymerization to provide crosslinking. The physical form of the polymer may be pellets, beads, emulsion, solution, or chunks. The polymer may have a molecular weight of from 5,000 to 5,000,000, preferably 10,000 to 2,000,000, more preferably 20,000 to 1,000,000 as determined by gel permeation chromatography (xe2x80x9cGPCxe2x80x9d). The polymer may have a melting point of from 20xc2x0 C. to 110xc2x0 C. as determined by differential scanning calorimetry (xe2x80x9cDSCxe2x80x9d). Alternate processes may be used to prepare the polymer of this invention. Suitable processes include solution polymerization, aqueous suspension polymerization, and aqueous dispersion polymerization (both batch and semi-continuous).
In the slurry process of the invention, a slurry is formed by cooling a solution containing the SWM and a solvent until the SWM precipitates out of solution as crystals. This process may be used for solution or suspension polymerization. For a solution process embodiment, the SWM may be admixed with an organic solvent and heated until the SWM is melted and dissolved, and then cooled with agitation. Suitable solvents include, but are not limited to hexane, heptane, xylene, toluene, ethyl acetate, butyl acetate, hexanol, heptanol, octanol, decane, decalin, and the like. After cooling, other monomers may be added. Suitable monomers include (meth)acrylic acid, esters of (meth)acrylic acid, (meth)acrylic amides, vinyl aromatic monomers, substituted ethylene monomers, functional monomers with a post crosslinkable group, multifunctional monomers, and mixtures thereof. The cooled slurry can be gradually added to a reaction kettle in the presence of an initiator to form solution polymers.
For a suspension process embodiment, the SWM may be admixed with other monomers and an aqueous solution and heated until the SWM is melted and dissolved in the organic phase. The mixture is cooled below the temperature at which polymerization will be initiated and then initiator is added. The mixture is stirred to evenly incorporate the initator into the organic phase. The cooled mixture containing the initiator is then heated and the stirring rate is increased to form a dispersion and to initiate polymerization. The aqueous solution may contain a suspending agent/dispersant for stabilizing polymerizing droplets. The suspending agent/dispersant may be used at from 0.01% to 5% by weight, based on the total weight of the mixture. Suitable suspending agents/dispersants include polyalkyldimethylammonium chloride, polyvinylalcohol, hydroxyethylcellulose, hydroxypropylcellulose or various other cellulose materials, polyvinyl pyrrolidone, natural gum, powdered dispersants, and the sodium salt of poly(meth)acrylic acid homopolymer or copolymers.
In the dispersion process of the invention, a solution containing a SWM in at least one second monomer is provided. In the process, the solution may be obtained by heating an admixture of a SWM in at least one second monomer until the synthetic wax monomer melts and dissolves as described above. The solution may be admixed with a second aqueous surfactant solution to create a monomer emulsion.
In one embodiment of the dispersion process, the at least one second monomer of the first solution may be selected from the monomers described above, including (meth)acrylic acid, esters of (meth)acrylic acid, (meth)acrylic amides, vinyl aromatic monomers, substituted ethylene monomers, functional monomers with a post crosslinkable group, multifunctional monomers, and mixtures thereof.
In a second embodiment of the dispersion process, the at least one second monomer of the first solution may be selected from a SWM containing polyethylene blocks. In this case, the second SWM acts as an aqueous dispersant for the first SWM. SWMs such as poly(ethylene-b-ethyleneoxide)-acrylate (Unithox(trademark) 450 acrylate), may be suitable for these purposes. Similar low molecular weight diblock polymers without the polymerizable (meth)acrylate end group, such as poly(ethylene)-b-poly(ethyleneoxide)-OH (Unithox(trademark) ethoxylate), may also be used as dispersants. The dispersants may be used at from 0% to 20% by weight, preferably 1% to 15% by weight, more preferably 2% to 10% based on the total weight of the first synthetic wax monomer.
For both dispersion process embodiments, the second solution may be an aqueous surfactant solution. Surfactants may be used at from 0.1% to 5% by weight, based on the total weight of the monomer mixture. The surfactants can be anionic, nonionic or cationic. Anionic surfactants or a combination of an anionic surfactant with a nonionic surfactant are preferred.
In the processes of the invention, a reaction mixture is formed by admixing at least one second monomer with the SWM. The amount of the at least one second monomer admixed with the SWM ranges from 50% to 99%, preferably 60% to 97%, more preferably 65% to 95% by weight based on the weight of the SWM. The at least one second monomer to be admixed with the synthetic wax monomer may be selected from the monomers described above, including (meth)acrylic acid, esters of (meth)acrylic acid, (meth)acrylic amides, vinyl aromatic monomers, substituted ethylene monomers, functional monomers with a post crosslinkable group, multifunctional monomers, and mixtures thereof.
In the processes of the invention, the monomers may be polymerized by co-feeding the reaction mixture and an initiator to a reactor or batch polymerizing a reaction mixture in a reactor at a temperature sufficient to initiate polymerization. Typically, the reactor is at a temperature from 75xc2x0 C. to 110xc2x0 C. The initiator is preferably water insoluble and may be selected from peroxyesters, dialkylperoxides, alkylhydroperoxides, persulfates, azoinitiators, redox initiators and other known free radical initiators. Part of the initiator is incorporated into the polymer as end groups. The amount of the initiator used is generally from 0.05% to 5% by weight, based on the weight of total monomer.
The dispersion process will yield a latex polymer. The polymer from the latex can be isolated by any method known in the art, such as spray drying, freeze drying, or coagulation. The suspension process will yield polymer beads. The polymer beads can be isolated by filtration. The solution process will yield a homogeneous polymer solution when a good solvent is used. Toluene, xylene, and decalin are examples of good solvents. If one wants to isolate the polymer from solution, one would use a poor solvent. By poor solvent is meant that the polymer is soluble in the solvent at high temperature, but insoluble at low temperature. Examples of poor solvents are heptane, hexane, or other saturated alkane solvents. The polymer may be isolated by cooling of the solution followed by filtration. Where a solid is isolated, the solid may contain solvent and may be vacuum dried at ambient temperature to give neat polymer chunks. The crumbly solid may also be diluted in solvent, re-heated to form a solution, cooled with stirring, vacuum filtered, and air dried on a Buchner funnel to yield solid polymer chunks.
Chain transfer agents may be used for regulating molecular weight in the processes to prepare the polymers of this invention. Suitable chain transfer agents include organic thiol compounds such as n-dodecyl mercaptan and the like. The chain transfer agent may be used at 0% to 10% by weight of the total monomer mixture. When used in the processes to prepare the polymers of this invention, part of the chain transfer agent structure is incorporated into the polymer as an end group.
A salt may be used in suspension processes of preparing the polymers of this invention to reduce the solubility of organic monomers in the aqueous phase. The salt may be used at from 0% to 8% by weight, based on the total weight of the mixture. Suitable salts include sodium chloride, potassium chloride and the like.
Organic solvents may be used in suspension processes of preparing the polymers of this invention for improving the solubility of the synthetic wax (meth)acrylate in the other monomers. The organic solvents may be used at from 0% to 200% by weight, preferably 0% to 100% by weight, based on the total weight of the synthetic wax (meth)acrylate.
A buffer may be useful in dispersion processes to prepare the polymers of this invention to maintain the pH of the aqueous phase. Suitable buffers include sodium, potassium, and ammonium salts of carbonate, bicarbonate, acetate, phosphate, and borate. The buffers may be used at from 0% to 5% based on the total weight of the composition.
Sodium nitrite or sodium perborate may be useful as radical inhibitors in dispersion processes to prepare the polymers of this invention to inhibit any undesirable polymerization in the aqueous phase. The radical inhibitors may be used at from 0% to 1% based on the total weight of water in the composition.
The polymers prepared by the process of the invention are useful in applications such as hot melt adhesives, hot melt sealants/caulks, plastic additives, compatibilizers, textile binders, roof mastics, traffic paints, barrier or protective coatings, powder coatings, water resistant sealer for wood and masonry materials, floor wax, water repellants for textiles, carrier polymers of biocides or other active ingredients in agriculture products.
For use in the above coating applications, the polymer may be formulated with materials such as binders, pigments, additives and fillers to prepare coating compositions suitable for each application. The coating composition is then applied to a substrate and then dried. The coating composition may be applied by spraying, dipping, or other methods known in the art. Suitable substrates include vinyl, polypropylene, metal, wood, cement, paper, nonwovens, textiles, and other substrates known in the art. The coating composition may be dried under ambient conditions. Forced air may be utilized to aid in the drying of the coating composition. Heat may also be utilized in the drying of the coating composition. The forced air may be heated, or the coated substrate may be placed in a heated oven. The temperature of the heat may range from 35xc2x0 C. to 110xc2x0 C.
The polymers of this invention may also be useful as dry powder coating compositions. For dry powder coating compositions, the polymer is isolated as a solid by the techniques described above. The dry polymer may be ground to a powder by any milling equipment suitable for producing particles in the size range of 0.1 to 50 microns, more preferably 0.25 microns to 35 microns, and most preferably from 0.5 microns to 25 microns. The particle size may be measured on a Coulter(trademark) LS, light scattering, particle size analyzer. Suitable mills are attrition mills, fluid-energy mills, colloid mills, vibratory ball mills (vibro-energy mills), pin mills, ball mills, roller mills, and autogenous and semiautogenous mills. Likewise a combination of mills could be used to possibly increase speed where the first mill reduces particle size to, for example, 100 to 1000 microns and a second mill reduces the particle size further to the desired range. An example would be the initial use of a hammer mill followed by a semiautogenous mill like a Dyno-Mill(trademark) from CB Mills Inc (Buffalo Grove, Ill.).
The dry powder may be applied to a substrate, heated to form a film, and cooled. Suitable substrates include vinyl, polypropylene, metal, wood, cement, paper, nonwovens, textiles, and other substrates known in the art. The dry polymer powder may be heated at temperatures ranging from 60xc2x0 C. to 150xc2x0 C. to form a film. The film may then be cooled either by storage at ambient temperature or by the use of cooled forced air.
The polymer may also be useful as an adhesive. For adhesive applications, a first polymer coated substrate is formed by applying the polymer to a substrate such as vinyl, polypropylene, metal, wood, cement, or paper. The polymer may be in the form of a liquid or a solid. For a solid polymer, the polymer is then heated to the melting point of the polymer. A second substrate may then be applied to the first polymer coated substrate. The second substrate may be selected from vinyl, polypropylene, metal, wood, cement, paper, or release paper. The polymer is then dried or cooled. The polymer may be dried under ambient conditions. Forced air may be utilized to aid in the drying of the coating composition. Heat may also be utilized in the drying of the coating composition. The forced air may be heated, or the coated substrate may be placed in a heated oven. The temperature of the heat may range from 35xc2x0 C. to 110xc2x0 C. The polymer may be cooled either by storage at ambient temperature or by the use of cooled forced air.